Migration-based Location Method Applied to a Perforation Shot Using LoFS Data at the Ekofisk Field, Norway

In this study we have analyzed passively recorded data utilizing the Life of Field Seismic (LoFS) system at the Ekofisk field in the North Sea. The system recorded a perforation shot consisting of 1.6 kg explosives (corresponding to about a moment magnitude of Mw 0) at about 2.1 km depth below seabed. To confirm the location of the perforation shot, the application of a very detailed, anisotropic 3D P-wave velocity model was required. Applying envelopes in the stacking operation eliminates the need for signal coherence across the array and results in robust location estimates for events with signal-to-noise (SNR) values clearly above 1, but fails at lower SNR. Limiting the number of data channels may be desirable for automatic real-time analysis although the reduced noise suppression will exacerbate the problems generated by, for example, airgun signals. Such existence of seismic shooting significantly disturbs the processing, reducing the detection threshold, and potentially introducing false triggers.